This is incredibly cool and I want to go build one, though it feels like that cutaway model of injecting the ultrasound from the side would lead to very uneven extraction.
I also chuckled at graf about doubling the caffeine content, as if that's necessarily a good thing =).
Those cheap HC-SR04 ultrasonic modules output at 40kHz, so maybe this is home-brewable.
The embedded youtube video at 0:58 shows a laptop screen with some pretty fancy-looking simulation jiggles and heatmaps on what looks like an espresso filter.
It also looks like a PDF of a paper, so presumably they have a paper that talks about the geometry/frequency interactions.
The article includes a link to the paper, which has simulation models of the acoustics, showing pressure levels and areas where cavitation can occur. (I didn't see anything about heating from dissipating the acoustic energy, though?)
I also chuckled at graf about doubling the caffeine content, as if that's necessarily a good thing =).
Those cheap HC-SR04 ultrasonic modules output at 40kHz, so maybe this is home-brewable.